1. Field of the Invention
The invention relates to an adjustable wrench which permits its sliding jaw to lock into different positions according to various nut or bolt sizes.
2. Description of the Related Art
Numerous situations exist in which it is advantageous to have an adjustable wrench that is capable of locking its sliding jaw. The most common situations occur in the maintenance field in which a mechanic needs to twist or turn nuts or bolts of varying sizes without having to readjust the setting of the wrench. Use of an adjustable wrench with a sliding jaw which is locked into position by nuts or bolts of different sizes avoids the problems that may be caused when attempting to conduct maintenance on large or elaborate machines with bolts or nuts which are not directly or easily accessible.
Various locking mechanisms have been devised for adjustable wrenches. U.S. Pat. No. 2,905,037, issued to Coslow on Sep. 22, 1959, discloses a worm locking means for an adjustable jaw wrench. The mechanism works on the principle that the more force placed on the jaws, the more securely the jaws lock into place. The jaw is "locked" by means of moveable V-shaped teeth in the worm that are urged against fixed V-shaped teeth in the frame. The teeth in the wrench have a high wear potential and will quickly lose their ability to "click" in adjustment. Further, if the wrench is jarred, the position of the jaws can easily change since the teeth will jump into a new position.
U.S. Pat. No. 5,154,103, issued to Lewis on Oct. 13, 1992, describes a lock for an adjustable wrench employing an elongated slide and a worm wheel with inner and outer surfaces which frictionally prevent the movement of the sliding jaw, thus locking the jaw into place.
U.S. Pat. No. 4,106,372, issued to Miller on Apr. 12, 1977, discloses an adjustable end wrench with a fixed jaw, a movable jaw and a locking means. The locking means is provided by a latch with a protrusion which selectively engages a groove on the movable jaw which prevents the jaw from moving any further. The lock provided on the movable jaw results from the mating of the teeth of the movable jaw with those on the latch. This approach also relies on the use of friction between the teeth on the latch and the teeth on the movable jaw to selectively lock the jaw into the desired position.
U.S. Pat. No. 4,454,791, issued to Seward, discloses a lockable adjustable wrench with a lock member that simultaneously engages a rack gear and a rotatable gear on the wrench. This approach relies on the frictional locking action that occurs when the teeth on the lock member, the rack gear and the rotatable gear are meshed together to prevent the sliding jaw from moving any further.
U.S. Pat. No. 4,326,436, issued to McGraw on Apr. 27, 1982, describes a combination adjustable/lockable/measuring wrench having a fixed jaw, a sliding jaw and preset means for locking and unlocking the location of the sliding jaw. The locking means used requires a brake which is selectively actuated by the use of a translatable push button to cause a tightening of a rotatable shaft and worm. The button rod engaged by the translatable push button increases the frictional tightness on the rotatable shaft. This approach relies on the use of friction between mechanical elements to prevent further movement of the sliding jaw.
U.S. Pat. No. 2,849,908, issued to Swanstrom et al. on Sep. 2, 1958, discloses an adjustable wrench that utilizes a specialized thumb wheel and a plate member with ears that attempts to lock the thumb wheel into position via a mushroom shaped pin. This design requires additional parts that must be carefully machined to exact tolerances thus substantially increasing the cost of manufacture. Also, to change the size of the wrench, the operator must release the plate member by compressing a spring while simultaneously turning the thumb wheel.
U.S. Pat. No. 1,498,656, issued to Herby on Jun. 24, 1924, discloses another adjustable wrench that attempts to retain the adjustment of the jaws. The thumb wheel is fitted with radiating grooves on the end facing the fixed jaw of the wrench. A pin in a pocket that is urged against a spring causes the pin to engage the grooves on the thumb wheel. The use of the pin causes wear to occur on the grooves which result in a loss of control after a period of time. Also, the use of only one side of the thumb wheel limits the number of fixed positions that can be obtained.
U.S. Pat. No. 3,857,308, issued to Lindgren on Dec. 31, 1974, discloses still another adjustable wrench. This disclosure attempts to solve the problem of the thumb wheel wearing against the mounting and the need for two different sized holes to mount the thumb wheel. In this disclosure, the thumb wheel is mounted via two ball bearings at opposing ends urged against the wrench frame via a single spring. A single hole drilled through the wrench frame serves to position the thumb wheel via the two balls engaging the bore of the hole.
A multi-position adjustable wrench that provides a constant locking force, having low wear characteristics, having sufficient adjustment capability to meet most standard sized nuts and points in between simply by rotating the thumb wheel is not found in the prior art.